1. Field of the Invention
This invention relates to luminescent complexes of lanthanide metals with imine ligands. It also relates to electronic devices in which the active layer includes a lanthanide complex.
2. Description of the Related Art
Luminescent compounds are of interest in a variety of applications, including analytical, bio-analytical and electronic uses. Extensive studies have been made of compounds of the lanthanide metals because of their characteristic sharp emission spectra with very narrow peak-widths. Analytical uses of luminescent complexes of lanthanide metals have been disclosed by, for example, Bell et al. in EP 556 005 and EP 744 451. Electronic devices using luminescent organometallic complexes of lanthanide metals have also been disclosed. In most devices the lanthanide centers are bound to diimine ligands, such as Skotheim et al., U.S. Pat. No. 5,128,587, and Bomer et al., U.S. Pat. No. 5,756,224. Heeger et al. have reported devices using europium complexes blended with semiconducting conjugated polymers (Adv. Mater. 1999, 11, 1349). Devices containing lanthanide centers bound to phosphineoxide ligands have been disclosed in, for example, Kathirgamanathan et al. WO 98/58037, Wenlian et al. Journal of the SID 1998, 6, 133, and Gao et al. Appl. Phys. Lett. 1998, 72, 2217.
There is a continuing need for improved luminescent lanthanide compounds. Futhermore, the synthesis and luminescent properties of lanthanide imine compounds have remained largely unexplored.